alright yesterday i was drivin around in my 97z. Usually the temp guage stays around 190 to 195 when driving and about 210-220 when idling at long stoplights. Well yesterday it heated up to the usual, hovered there for maybe less than a minute and began going up, it went up pretty high while i was driving but i turned the car off when it hit about 240. I was still on the road but i just coasted into a parking lot. when i pop the hood i found that my radiator cap had come off while i was driving, but the first thing i thought was that i had blown a head gasket. If the head gasket it is blown, shouldnt the coolant back up into the little fill tube? there was nothing in there when i checked that and the engine seemed fine after a visual inspection. i didnt try to start it again, but i turned the key to on to see what the temp was and it when down to normal in about an hour. anyway i figured that my t/stat had broken in the closed position and caused to much pressure in the radiator and the rest of the cooling system but im not exactly sure. im gonna go start it today and make sure it still runs ok b/c im not sure if any got on the distributor or not. HELP

 

I could have been that your radiator cap was not tight enough, did you change the radiator cap recently?? Also as coolant heats it expands and thats when coolant flows to the reservor, threw that little hose you mention ontop of tha ratiator neck.

 

mine did the same thing as you're where the coolant comes up to the resivour
see the forum entitled "overheating z28pete help" i ahve a picture, and if thats what you're talking about then you should be ok. my head gasket isnt blown. replace youre thermastat see what happens.
did your z always run hot at an idle?

 

It never ran hotter than 210 at idle, and no coolant came up in the reservoir like yours. That little tube by the battery was empty. I did go check it yesterday, there is a crack in the radiator it didnt hold any water at all, i did however start it up. It ran just fine, didnt sound bad or smell bad, the exhaust smelled normal and it revved up real strong so that made me feel a little bit better. Other than that my biggest problem now is transportation

 

I think thestuff is called 'bars leak'. Its a radiator treatment for leaks. I used it once on a 79 ford courier and it worked like a charm. I dont know how it will react with your radiator though. I would say that if nobody objects on here to give it a try.

 

I had similar problem with my 95z when I first got it. My hole was in the top as long as I kept the rpms up it was fine. There were plenty of pissed people at 4 in the morning.I couldn't find any one who would repair the plastic. I got lucky though a buddy of mine was junking one of his old cars and gave me the radiator

 

alright i got it back yesterday, turns out it was my cap that was broken.......it wouldnt hold any pressure so coolant would leak out and eventualy enough pressure simply blew it off they said; nothing to do with the t/stat. other than that, it would be rather obvoius if my headgasket was blown right? it seems to be runnin well again, but im gonna be watchin the distributor real close